Considerable attention has been focused in recent years on intravenous and intraarterial delivery of fluids to patients. Precision control over the rate at which such parenteral delivery occurs is of critical importance, inasmuch as improper administration of fluids can retard the recovery of patients or, in extreme situations, lead to further injury or even death. Early parenteral delivery systems relied on gravity flow to transfer fluid from a fluid container or reservoir to the patient. Attempts to accurately regulate gravity flow, however, proved difficult because the pressure forcing the fluid between the reservoir and the patient decreased as the fluid level within the reservoir dropped during the delivery operation. Thus, delivery rates in gravity-flow systems tended to vary in an unacceptable manner.
More recent parenteral delivery systems have employed pump motors in an effort to increase fluid delivery rate accuracy. Often, the pump motors comprise stepping motors which drive plunger or piston-like fluid pumps in response to suitable stepping motor control procedures. These procedures are highly compatible with the precision control requirements of parenteral administration because they provide the necessary degree of accuracy and are capable of implementation through reliable and efficient microprocessor programming techniques. U.S. Pat. Nos. 4,037,598 issued to Georgi on July 26, 1977; 3,994,294 issued to Knute on Nov. 30, 1976; 3,985,133 issued to Jenkins et al on Oct. 12, 1976, and 3,736,930 issued to Georgi on June 5, 1973 all disclose intravenous delivery systems wherein stepping motors are utilized in conjunction with camming mechanisms and pumping structures to achieve accurate delivery rate control. Despite the advantages offered by prior art systems, however, certain improvements in the delivery of fluid from a stepping motor-driven fluid pump can be made. For example, it is highly beneficial to provide some means for monitoring the operation of the stepping motor in order to insure that the stepping motor does not "run-away" or deviate from a preselected operating speed by more than a predetermined amount. In this manner, over- or under-delivery of fluid to the patient, as well as the risk of serious injury attendant therewith, can be avoided.